Chapter 2: Git, GitHub and Git Bash

2.4 Install check and first vocabulary

By Ravindra Bagale · Last updated: 25 October 2026

Why: the problem

On your first day at a new job, the laptop is fresh. Before you write one line of code, Git must be installed and set up. If you skip setup, every commit will say "root" or a random name, and your manager cannot see who did the work. Some companies even block pushes when the email does not match the company email. In this lesson you will install Git on Ubuntu, Windows and Mac, check the version, set your name and email, choose a default branch name and editor, and learn the first words you will hear every day: working tree, staging area, commit, branch and HEAD. These words come again in every later lesson, so learn them here with real commands, not just definitions.

What we will build

You will install Git, write a clean global config, see where Git stores it, and make one test repo where you can point to the working tree, the staging area, a commit, a branch and HEAD with a real command each.

What: every term in plain English

• git config --global — Settings for your user, saved in ~/.gitconfig.
• git config --local — Settings for one repo only, saved in .git/config.
• user.name and user.email — The author shown on every commit.
• init.defaultBranch — The branch name for new repos. Most teams use main.
• core.editor — The editor Git opens for messages, like nano or VS Code.
• Working tree — Your normal files.
• Staging area (index) — The list of changes picked for the next commit.
• HEAD — A pointer to the commit you are on now.

How: step by step

1. Install on Ubuntu

   sudo apt update && sudo apt install -y git
   

   What it does: Installs Git from Ubuntu packages.

   Output

   Setting up git (1:2.43.0-1ubuntu7) ...
   

2. Install on Windows

   Download Git for Windows, keep the defaults, finish
   

   What it does: Also installs Git Bash.

   Output

   Git for Windows 2.47 installed
   

3. Install on Mac

   xcode-select --install   (or: brew install git)
   

   What it does: Mac has Git with the developer tools.

   Output

   git version 2.39.5 (Apple Git-154)
   

4. Check the version

   git --version
   

   What it does: Version 2.30 or newer is fine for this course.

   Output

   git version 2.43.0
   

5. Set name and email

   git config --global user.name "Ravi Learner" && git config --global user.email "ravi@example.com"
   

   What it does: Use your work email at a job.

   Output

   (no output)
   

6. Set branch name and editor

   git config --global init.defaultBranch main && git config --global core.editor nano
   

   What it does: New repos start on main. Messages open in nano.

   Output

   (no output)
   

7. List the config

   git config --global --list
   

   What it does: Check every value once.

   Output

   user.name=Ravi Learner
   user.email=ravi@example.com
   init.defaultbranch=main
   core.editor=nano
   

Example 1: Write a full starter config for a new laptop

Stack. Git

Goal. Write a full starter config for a new laptop.

~/.gitconfig

[user]
    name = Ravi Learner
    email = ravi@example.com
[init]
    defaultBranch = main
[core]
    editor = nano
    autocrlf = input
[pull]
    rebase = true
[alias]
    st = status -sb
    lg = log --oneline --graph --decorate -15

What each line does

• [user] — Author for all commits.
• defaultBranch = main — No more master by default.
• autocrlf = input — Fixes Windows line endings when you commit.
• pull.rebase = true — git pull keeps history straight.
• st and lg — Short aliases for daily commands.

Green output

$ git st
## main
$ git lg
* 3f2a1c9 (HEAD -> main) First commit

Expected result. One file makes every new repo behave the same. Many teams share a starter file like this.

Example 2: Point to the working tree, staging area, commit and HEAD

Stack. Git

Goal. Point to the working tree, staging area, commit and HEAD.

vocab.sh

mkdir -p ~/devops-lab/vocab && cd ~/devops-lab/vocab
git init -q
echo "hello" > a.txt
git status --short
git add a.txt
git status --short
git commit -qm "Add a.txt"
git log --oneline
cat .git/HEAD
git branch

What each line does

• ?? a.txt — In the working tree, not tracked yet.
• A a.txt — Added to the staging area.
• git commit — Staged change becomes a commit.
• cat .git/HEAD — HEAD points to the branch main.
• git branch — The star shows your current branch.

Green output

?? a.txt
A  a.txt
8a1b2c3 Add a.txt
ref: refs/heads/main
* main

Expected result. Each word now has a command you can show. That is how you explain it in an interview.

Example 3: Use a different email for work repos only

Stack. Git

Goal. Use a different email for work repos only.

work-email.sh

mkdir -p ~/devops-lab/work-repo && cd ~/devops-lab/work-repo
git init -q
git config --local user.email "ravi@company.example.com"
git config user.email
git config --show-origin user.email
git config --global user.email

What each line does

• --local — Only for this repo.
• git config user.email — The value Git will really use here.
• --show-origin — Which file the value comes from.
• --global user.email — Your personal email stays for other repos.

Green output

ravi@company.example.com
file:.git/config    ravi@company.example.com
ravi@example.com

Expected result. Work commits use the work email, home projects use the home email.

Example 4: Set up Git inside a clean Ubuntu container, like a fresh CI runner

Stack. Docker, Ubuntu 24.04, Git

Goal. Set up Git inside a clean Ubuntu container, like a fresh CI runner.

fresh-runner.sh

docker run --rm -it ubuntu:24.04 bash
apt update -qq && apt install -y -qq git
git --version
git config --global user.name  "CI Bot"
git config --global user.email "ci@example.com"
git config --global init.defaultBranch main
git config --global --list
mkdir /work && cd /work && git init -q && git status

What each line does

• docker run --rm -it ubuntu:24.04 bash — A brand new Linux with nothing set up, deleted on exit.
• apt install -y -qq git — Install Git quietly.
• git config --global ... — A CI runner also needs a name and email to make commits.
• git init -q && git status — Proves Git works in the new machine.

Green output

git version 2.43.0
user.name=CI Bot
user.email=ci@example.com
init.defaultbranch=main
On branch main
No commits yet
nothing to commit (create/copy files and use "git add" to track)

Expected result. Jenkins agents and GitLab runners start like this. If a pipeline says "Please tell me who you are", this is the missing step.

Verify: did it work?

1. Check version

   git --version
   

   What it does: Git is ready.

   Output

   git version 2.43.0
   

2. Check author

   git config user.name; git config user.email
   

   What it does: Both must print values.

   Output

   Ravi Learner
   ravi@example.com
   

3. Check default branch

   git config --global init.defaultBranch
   

   What it does: Should be main.

   Output

   main
   

When it is red 1

hint: Using 'master' as the name for the initial branch.

Cause. init.defaultBranch is not set.

Fix, step by step

1. git config --global init.defaultBranch main
2. For this repo: git branch -m master main

When it is red 2

error: cannot run vim: No such file or directory

Cause. Git tries an editor that is not installed.

Fix, step by step

1. git config --global core.editor nano
2. Or use git commit -m "message".

When it is red 3

warning: in the working copy of 'app.sh', LF will be replaced by CRLF

Cause. Windows line ending setting.

Fix, step by step

1. git config --global core.autocrlf input
2. Add a .gitattributes file with * text=auto.

Cleanup

1. Remove test repos

   rm -rf ~/devops-lab/vocab ~/devops-lab/work-repo
   

   What it does: Your global config stays.

   Output

   (no output)
   

Practice tasks

Homework: try at home

Recap

• Install Git with apt, Git for Windows, or xcode tools.
• Set user.name, user.email and init.defaultBranch first.
• Global config is ~/.gitconfig; local is .git/config.
• Working tree, staging area and commit are the three places.
• HEAD shows where you are now.

FAQ

Do I need the newest Git?

No. 2.30 or newer is enough.

Can I change my name later?

Yes, for new commits. Old commits keep the old name.

Should I use my personal email at work?

No. Use the company email in work repos.

What is the index?

Another name for the staging area.

Is VS Code fine as editor?

Yes: git config --global core.editor "code --wait".

Why does my pipeline say "Please tell me who you are"?

The runner has no user.name and user.email. Set them in the job before any commit.

Interview questions

1. How do you set up Git on a new machine?

   Install it, then set user.name, user.email, init.defaultBranch and an editor, and check with git config --list.

2. Difference between global and local config?

   Global applies to your user in ~/.gitconfig; local applies to one repo in .git/config and wins.

3. What are the three areas in Git?

   Working tree, staging area and the repository of commits.

4. What is HEAD?

   The current commit, usually via the current branch reference.

5. Why set core.autocrlf?

   To avoid line ending changes between Windows and Linux.

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